Skip to main content

Full text of "Text Book Of Mechanical Engineering"

See other formats

Time and Distance Bases.


velocity for the given position of crank, while the crank arm itself
gives W's velocity. Taking various positions of P on HJ, and
setting up the corresponding polar radii, the curve of P's velocity
is obtained as H K j, while the ordinates A w, set up dotted on a
base N o of half crank circle circumference, shew crank velocity.


Assuming P's pressure as uniform, the ordinates Im will give
a curve of pressure; and the AE ordinates, being transferred from
the polar curve to the base N o,. will give a curve of tangential
pressures on crank. Notice points Q R and s T, where P and W
have equal velocities, and also points F and w, where P has its
highest velocity, and W its greatest pressure

Time and Distance Bases.—The pfofile of velocity
curve depends on the terms in which we state the base-line
divisions. The curves in Fig. 434 are drawn with a time base
line (equal titties), but the oblique lines at c and D -would be
parabolas if a distance base (equal distances) were used. In
Fig* 453, K j is a distance base, but supposing NO to represent

L I.